Audio-frequency electromechanical vibrator

ABSTRACT

An audio-frequency electromechanical vibrator having a flat hollow case with a thin cover plate, a flat ring-shaped permanent magnet axially magnetized and a flat annular drive coil unit. The magnet and the coil unit are disposed in the case coaxial with one another and with an axial space therebetween. The magnet is fixedly mounted on the bottom of the case and the coil unit is elastically supported to the case by a spring plate so that the vibrator can generate strong vibrations without noise generation corresponding to a comparatively higher frequency component in an audio signal applied to the coil unit.

BACKGROUND OF THE INVENTION

(1) Field of the Invention

This invention relates to electromechanical vibrators and, inparticular, to audio-frequency electromechanical vibrators adapted for abody-felt vibration reproduction in sound reproducing systems.

(2) Description of the Prior Art

A sound reproducing system has been known in the prior art as disclosedin, for example, U.S. Pat. No. 4,064,376, which reproduces from anelectric signal not only sound heard by ear but also mechanicalvibration of, preferably undertones lower than 150 Hz, to be directlytransmitted to a body. Such a system has an electromechanical vibratorfor reproducing the mechanical vibration which is fitted to a bed or achair. An audio signal to be fed to sound reproducing speakers is alsoapplied to the vibrator, preferably after passing through a filter forremoving a higher frequency component than 150 Hz. A person on the chairor bed feels vibration while enjoying music from the speaker throughear.

An electro-dynamic transducer is used for the vibrators in such soundreproducing system, a known vibrator has an arrangement similar to anelectro-dynamic speaker, as shown in U.S. Pat. Nos. 4,064,376 and4,354,067. The known vibrator has a magnetic circuit constituted by oneor two permanent magnets and a magnetic yoke with a magnetic gap inwhich a drive coil is loosely fitted or disposed. The electric signal isapplied to the drive coil and therefore, the coil and the yoke are movedrelatively to cause the vibration.

In the known vibrator, the drive coil is disposed in a small magneticgap and therefore strong vibrations can not be generated. Furthermore, athin and good heat-conductivity case cover is required to make good heatradiation from the drive coil. This means that the case cover tends tovibrate in response to a higher frequency component included in theaudio signal applied to the vibrator, so that the vibrator makes noise.In order to prevent the noise generation, the filter must be used toremove the higher frequency component from the audio signal applied tothe vibrator.

SUMMARY OF THE INVENTION

It is an object of this invention to provide an audio frequencyelectromechanical vibrator which can make strong vibrations.

It is another object of this invention to provide a vibrator which doesnot vibrate in response to a higher frequency component included in anaudio frequency signal applied to the vibrator.

It is still another object of this invention to provide a vibrator witha reduced heat generation.

It is yet another object of this invention to provide a vibrator whichis generally flat and compact.

It is another object of this invention to provide a vibrator whereinheat generated is readily diffused.

It is still another object of this invention to provide a vibrator whichis simple in construction and assembling operation.

The present invention is an audio-frequency electromechanical vibratorcomprising an open-topped case of a magnetic material with a cover plateclosing the open end, an annular coil unit for receiving anaudio-frequency power signal and being disposed within the case, aring-shaped permanent magnet being axially magnetized, the ring-shapedmagnet disposed coaxial with the annular coil unit and facing the coilunit with an axial space therebetween, and a spring damper meanssupported in the case and for elastically supporting one of the magnetand the coil unit, the other one being fixedly mounted to an innerbottom of the case.

According to the present invention, a flat and compact vibrator can beobtained by the use of a flat hollow case, a flat coil unit and a flatmagnet. The vibrator can produce strong and neat vibration with areduced heat generation.

The vibrator according to the present invention can be driven by anaudio-frequency signal without the use of a filter for removing acomparatively higher frequency component, because neither coil unit normagnet is directly connected to a thin cover plate.

In an aspect of the present invention, the case has a central bossportion formed by a central portion of the bottom of the case beinginwardly raised. The coil unit and the magnet are disposed within anannular space around the central boss portion and coaxial with thecentral boss portion. A spring pale is supported on, and coaxial with,the central boss portion.

In another aspect of the present invention, the case has terminal platemeans having terminals to which leads of the coil unit are connected. Anelectrical cable can also be connected to the terminal means aftercompletion of assembling of the vibrator, to supply the audio signal tothe coil unit.

In still another aspect of the present invention, the case has aplurality of small holes for permitting air to flow therethrough, and asponge-like soft and porous member is disposed in the case to close thesmall holes.

Further objects, features and other aspects of the present inventionwill be understood from the following detailed description of preferredembodiments referring to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a sectional view of a known audio-frequency electromechanicalvibrator;

FIG. 2 is a partially exploded plan view of an embodiment according tothe present invention;

FIG. 3 is a sectional view of the embodiment taken along a line III--IIIin FIG. 2;

FIG. 4 is a perspective view of a chair using the vibrator, partiallyexploded for viewing the vibrator attached thereto;

FIG. 5 is a schematic circuit diagram view of a system driving thevibrator;

FIG. 6 is a sectional view of another embodiment of the presentinvention; and

FIG. 7 is a partially exploded plan view of the embodiment of FIG. 6,with a cover plate being removed.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Prior to description of preferred embodiments of the present invention,a known audio-frequency electromechanical vibrator is described inconnection with FIG. 1.

Referring to FIG. 1, a known audio-frequency electromechanical vibrator1 shown therein comprises a magnetic circuit constituted by a magneticyoke 2 of a inversed T-shape having a center pillar 2a and a bottomplate 2b, a ring-shaped permanent magnet 3 disposed on bottom plate 2b,and an annular top yoke plate 4 attached on permanent magnet 3. Anannular small space or a magnetic gap 5 is formed between a top portionof center pillar 2a and an inner end of annular plate 4. A drive coil 6is loosely fitted or disposed in the magnetic gap 5. The magneticcircuit structure is elastically supported by a case 7 through a springplate 8, and drive coil 6 is supported by a case cover 9 through a coilbobbin 10.

Since drive coil 6 is disposed in a static magnetic field generated inthe magnetic gap 5, drive coil 6 and the magnetic circuit structure(2-3-4) are relatively moved when an electric A.C. current is applied todrive coil 6. Thus, the vibrator 1 vibrates in response to an electricaudio signal applied to drive coil.

Since drive coil 6 is loosely fitted in the magnetic small gap 5, it isa small coil of a thin wire, so that a large current cannot be appliedto drive coil 6. Therefore, the known vibrator 1 has a problem that astrong vibrations cannot be generated, as described hereinabove.

In order to radiate heat generated by drive coil 6, case cover 9 is madeof a thin and good heat conductivity material. This means that coverplate 9 vibrates in response to a higher frequency component included inan audio-frequency signal applied to the vibrator to make noise, asdescribed hereinabove. Therefore, a filter must be used before theaudio-frequency signal is applied to the vibrator.

The present invention resolves such problems and provides an improvedaudio-frequency electromechanical vibrator.

Referring to FIGS. 2 and 3, a vibrator 11 according to a embodiment ofthe present invention has a opentopped case 12 of a magnetic materialand a cover case 13 closing the open top end of the case 12.

A ring-shaped permanent magnet 14 axially magnetized is fixedly mountedonto an inner bottom surface of case 12. An annular coil 15 is disposedto face magnet 14 with a space therebetween. The annular coil 15 iscontained in an annular coil housing 16 of a magnetic material. The coil15 is secured to coil housing 16 by, for example, adhesive agent to forma coil unit. The coil housing 16 is fixed to a spring plate 17 which isfixedly secured to case 12, so that the coil unit is elasticallysupported by spring plate 17 in case 12.

An electric cable 18 is led into case 12 through a hole 13a formed incase cover 13 and is electrically connected to coil 15. A gum bushing 19is fitted in hole 13a to hold electric cable 18.

Case 12 has an outer annular flange portion 12a to which a vibrationplate 20 is joined.

In the arrangement of vibrator 11, since an axial end of ring-shapedpermanent magnet 14 faces to an axial end of annular coil 15, the coilunit (15-16) including coil 15 moves axially in relation to case 12having magnet 14 at a time when an electric current is applied to coil15. Thus, application of audio signal to coil 15 axially drives the coilunit (15-16) reciprocatively to make vibration corresponding to theaudio signal.

Since coil unit (15-16) faces an axial end of ring-shaped magnet 14 andis disposed in a large space in case 12, a large coil can be used in thevibrator which has a large number of windings and made of a thick wire.Therefore, the vibrator can generate strong vibrations with a reducedheat generation.

It will be understood that the vibrator can be made flat and compact bythe use of a flat coil unit and a flat magnet.

Furthermore, since cover plate 13 is not directly connected to coil 15and magnet 14 which are relatively moved, it is not directly vibrated bycoil 15 or magnet 14. Therefore, cover plate 13 does not generate noiseeven if it is made of a thin and good heat-conductivity plate. Thismeans that a filter is not necessary for removing a higher frequencycomponent from an audiofrequency signal applied to the vibrator.

The vibrator is adapted to, for example, a chair.

Referring to FIG. 4, vibrator 11 is mounted in a chair back 21a of achair 21 by securing vibration plate 20 to a cushion spring 22 in thechair back by, for example, strings or tapes 23.

A person on the chair 21 feels vibration at his back when an audiosignal is applied to the vibrator 11.

Referring to FIG. 5, a right channel (R) signal and a left channelsignal (L) are applied to respective speakers 24R and 24L from an audiosignal amplifier (not shown). The R and L signals are also inputted intoa mixer circuit 25. The output signal from mixer 25 is applied to coil15 of vibrator 11 through a filter 26 and a power amplifier.

Filter 26 is for removing a frequency component lower than 99 Hz fromthe output of mixer 25 because a lower frequency signal is consideredunpleasant.

Referring to FIGS. 6 and 7, another embodiment 11' shown therein issimilar to the vibrator 11 in FIGS. 2 and 3 but is different therefrom,mainly, in support of the coil unit. The similar parts are representedby the same reference numerals as FIGS. 2 and 3, and a detaileddescription thereto is omitted for purpose of simplification of thedescription.

A central portion of a bottom of a case 12' is raised upwardly so thatthe case 12' is formed to have a cross section of a W-like shape. Thus,the case has a central boss portion 12'a.

Ring-shaped permanent magnet 14 and the coil unit (15-16) are disposedin an annular space around the central boss portion 12'a. Magnet 14 isfixedly mounted on the inner bottom of case 12', and coil unit (15-16)faces magnet 14 with a space therebetween. Coil unit (15-16) is fixed toa spring plate 17'.

Spring plate 17' is fixedly secured to boss portion 12'a by joining acentral portion of spring plate 17' to the top end of the boss portion12'a by, for example, a rivet 28, so the boss portion 12'a, spring plate17' and coil unit (15-16) are disposed coaxially. Thereby, coil unit15-16 can vibrate uniformly.

Terminal plates 29a and 29b are mounted in an annular wall of bossportion 12'a, and lead wires 15a and 15b are connected to terminals 30aand 30b of terminal plates 29a and 29b. Electric cable 18 is led out tothe back side of the case 12' through gum bushing 19 and a central holeof rivet 28, and is connected to terminals 30a and 30b, as shown in FIG.6. Thus, electric cable 18 can be fixed to case 12' and electricallyconnected to coil 15 without removal of case cover 13 after the vibratoris completely assembled.

A ring shaped felt pad 31 is overlaid onto magnet 14 to form a bufferbetween the magnet and the coil unit (15-16).

Furthermore, a ring member 32 of a soft and porous, such as sponge-likematerial is disposed around magnet 14 to serve as another buffer betweenmagnet 14 and the coil unit (15-16).

Case 12' is provided with a number of small holes 12'b along the ringmember 32 so that holes 12'b are closed by the ring member. Air in thecase 12' is exchanged through the holes 12'b and the sponge-like ringmember serves as a filter for removing dust.

Outer circumference flange portion 33 and 34 of case 12' and case cover13' are joined and are together secured to a vibration plate 20' byscrew means. Vibration plate 20' is of a hard material, and may bebacked with another plate 35 of a soft material.

In the above described embodiments, the permanent magnet is fixedlymounted to the case and the coil unit is elastically supported by thespring plate. However, it will be easily understood that the magnet andthe coil unit may be mounted to the spring plate and the case,respectively.

What is claimed is:
 1. An audio frequency electromechanical vibratorcomprising:an open-topped flat case of a magnetic material with a coverplate closing the open end; a annular drive coil unit for receiving anaudiofrequency power signal and being disposed within said case, saidcoil unit comprising a annular coil housing of magnetic material with anopen axial end and a coil contained in, and fixed to, said coil housing;a flat ring-shaped permanent magnet having an axial end and beingaxially magnetized, said ring-shaped permanent magnet being disposedcoaxial with, and adjacent, said annular coil unit in an axial directionso that said axial end of said permanent magnet faces said open axialend of said coil housing with an axial gap left therebetween; and aspring damper plate being supported in said case for elasticallysupporting one of said coil unit and said magnet, the other one of saidcoil unit and said magnet being fixedly mounted to an inner bottom ofsaid case.
 2. The vibrator as claimed in claim 1 wherein said coverplate is made of a thin and good heat-conductivity plate.
 3. Thevibrator as claimed in claim 1, which further comprises a ring-shapedbuffer means overlaid onto said axial end of said magnet.
 4. Thevibrator as claimed in claim 1, wherein said case is provided with aplurality of small holes, a sponge-like soft and porous member beingdisposed in said case to close said holes.
 5. The vibrator as claimed inclaim 1, wherein said case has a central boss portion which is inwardlyraised continuous with a bottom portion of said case, said spring platebeing supported onto a top end of said central boss portion.
 6. Thevibrator as claimed in claim 5, wherein said magnet and said coil unitare disposed in an annular space around said central boss portion andcoaxial with said boss portion and said spring plate.
 7. The vibrator asclaimed in claim 5, which further comprises terminal plate means mountedin a wall portion of said boss portion, electric terminal means mountedon said terminal plate means, electric lead wires of said coil beingconnected to said electric terminal means, and an electric cable forsupplying said audio-frequency power signal to said coil and beingconnected to said terminal means.
 8. The vibrator as claimed in claim 7,wherein said cover plate has a central hole, said central boss portionhaving a central hole, said electric cable being led to a back side ofsaid case through said central portion.
 9. The vibrator as claimed inclaim 4, wherein said magnet is fixedly mounted onto a bottom plate ofsaid case, said small holes being located around said magnet, saidsponge-like member being formed annular and being disposed around saidmagnet.
 10. The vibrator as claimed in claim 1, which further comprisesan outer annular flange formed on said case, wherein a vibration plateis fixed to said flange.
 11. The vibration as claimed in claim 10, whichfurther comprises a soft material plate mounted as a backing to saidvibration plate.